"Our study showed that the characteristics and cover of the fuel closest to houses was more important than the effects of prescribed burning in reducing house loss," says Cary.

On 7 February 2009 more than 2000 homes were destroyed in a series of intense bushfires in southern Australia.

The so-called Black Saturday fires provided a rare opportunity to research the relative importance of different factors, especially bushfire fuel, in determining whether or not a house survives a fire.

Cary and colleagues looked at tree cover and type, the amount of prescribed burning, the distance between houses, the fire weather and the slope of the terrain.

"We used statistical modelling to determine the relative importance of these factors in determining whether a house was lost during the Black Saturday fires," says Cary.

The study, which involved 12,000 measurements from 500 houses affected by the fire, found that clearing trees from around a house was the most effective way of reducing this risk.

"Clearing vegetation around houses was at least twice as effective as recent prescribed burning in the near vicinity for protecting houses on Black Saturday," says Cary.

The researchers found tree cover close to houses varied from 90 per cent down to nearly zero.

When native tree cover was high, the probability of house loss was 60 per cent and this reduced to 30 per cent as the cover was reduced to zero, says Cary.

"Our study showed that the higher the cover of vegetation within 40 metres of a house, the higher the likelihood that it was destroyed," he says.

"There were a large number of houses which had high levels of tree cover and may not have been lost in those fires if the tree cover had been reduced."

Strategy

With the loss of life and property from bushfires forecast to increase due to population growth and climate change, there has been an increased effort to reduce available fuel.

Cary says there needs to be a shift away from broad-scale fuel reduction and a focus on removing fuel close to properties.

"The focus of prescribed burning is generally further away from houses," says Cary.

The new study found prescribed burning is likely to be most effective when carried out close to the house - as close as 500 metres, rather than many kilometres away.

It found that recent prescribed burning close to the house reduced the chance of house loss by 15 per cent, compared to prescribed burning that had been undertaken many kilometres away.

Vegetation choice

Cary acknowledges that many people are unlikely to clear all the trees around their house for aesthetic reasons or to preserve biodiversity or privacy.

He points out the probability of house loss was lower for planted vegetation, than for remnant native vegetation.

The research found a high cover of planted vegetation near the house correlated with a 40 per cent chance of the house being lost.

As the level of this vegetation cover approached zero, this risk fell to below 20 per cent.

Bushfire Urban Design expert Justin Leonard of CSIRO's Climate Adaptation Flagship agrees careful plant selection and garden design is important, and recommends using plants with low flammability that suit the local climate and if possible are native to the area.

He says people can consider using tools such as the CFA plant key to design their gardens.

Leonard says it is also important to design and maintain houses to protect them from embers and radiation.

But he agrees with Cary and team that the most effective thing to do is manage the vegetation around houses.

"The concept of vegetation closest to the building having the highest level of influence [on house loss] is highly consistent with our research," he says. "It is great to see other independent work confirming this."